Initiation method of a method for producing 2,2-bis(4-hydroxyphenyl)propane

ABSTRACT

A process for the commissioning of a process for the production of 2,2-bis(4-hydroxyphenyl)propane is disclosed. The process that entails reacting phenol with acetone in the presence of sulfonated cross-linked polystyrene resins is characterized in that the commissioning takes place with an acetone concentration reduced below, and a phenol concentration increased above, that of the optimal sustained operation state, with a reduced quantitative throughput, and in that with temperature control, the reactant quantity and the acetone content of the reactor feed are subsequently increased until the sustained operating state is reached.

The application relates to the commissioning of a process for theproduction of bisphenol.

Bisphenol production is known, and generally takes place by means ofacid-catalysed reaction of phenols with carbonyl compounds. The reactionis generally carried out in fixed bed or fluidised bed reactors, andalso in reactive columns.

Cross-linked sulfonated polystyrene resins (acid ion exchangers) arepreferably employed as catalysts. These ion exchangers may optionally bechemically modified by co-catalysts having covalent or ionic bonds, andare macroporous or in the form of a gel U.S. Pat. No. 4,191,843; U.S.Pat. No. 3,037,052).

For efficient and economic production of, for example,2,2-bis(4-hydroxyphenyl) propane (BPA) by reacting phenol with acetone,on the one hand the highest possible acetone conversions should beobtained at simultaneously high p,p-BPA selectivity as a result ofsuitable selection of the reaction conditions, and on the other hand itis crucial that the catalyst (ion exchanger) should maintain itsactivity over a long period in order to avoid costly catalystreplacement.

In the literature, therefore, increased attention is accorded in BPAproduction to the preparation and reactivation of catalysts.

Thus, EP-A 765 685 describes the way in which the previous washing anddewatering of commercial ion exchangers leads to greater product purity.EP-A 680 786 teaches that deactivated ion exchangers may be reactivatedby rinsing with anhydrous phenol at fairly high temperatures.

The object is an optimised commissioning of a continuous process for theproduction of BPA by reacting phenol with acetone in the presence ofsulfonated cross-linked polystyrene resins.

It has now surprisingly been found that the catalytic performance andservice life of the catalyst system is influenced by the total quantityof reaction mixture, on the one hand, and also in addition by thecomposition of the reaction mixture, on the other.

The present application therefore provides a process for thecommissioning of a process for the production of2,2-bis(4-hydroxyphenyl)propane by reacting phenol with acetone in thepresence of sulfonated cross-linked polystyrene resins, which ischaracterised in that

a) the commissioning takes place with an acetone concentration reducedbelow, and a phenol concentration increased above, that of the optimalsustained operation state, with a reduced quantitative throughput, and

b) with temperature control, the reactant quantity and the acetonecontent of the reactor feed are subsequently increased in step-wise orcontinuous manner until the sustained operating state is reached.

In principle, the condensation reaction between phenol and acetone maybe carried out with an acetone concentration of up to 15 wt. %. Whereashigh acetone concentrations lead to increased BPA production andconsequently to increased space-time yields, the heat liberated by thecondensation reaction may lead to industrial limitations. Moreover, anelevated acetone concentration leads to reduced selectivities in thereaction.

Preferably, when the reaction mixture is first contacted with thecatalyst system the acetone concentration is reduced by at least 30%,preferably at least 45%, below the acetone concentration which ispreferred in sustained operation. The total quantity of reaction mixtureis reduced by at least 40%, preferably at least 60%, below the quantitywhich is preferred in sustained operation.

The intake temperatures are preferably around 45 to 80° C., particularlypreferably around 50 to 65° C.

The temperature increase in the reactor is monitored by temperaturemeasurement points on the reactor. Here, temperatures of 110° C.,preferably 100° C., particularly preferably 90° C., should not beexceeded at each measurement point. The process is preferably managedsuch that a temperature peak travels through the reactor. When thetemperature peak reaches the reactor outlet, the acetone quantity in thefeed is then increased in continuous or step-wise manner up to theacetone concentration which is preferred in sustained operation.Simultaneously or preferably subsequently, the total quantity at thefixed bed reactor feed is increased in step-wise or continuous manner tothe total quantity which is preferred in sustained operation. Thereaction temperature is then optionally adjusted to the sustainedoperation temperature.

For sustained operation of BPA production phenol and acetone areutilised preferably in the ratio >5:1, particularly preferably >10:1.Here, acetone concentrations of from 2.0 wt. % to 15.0 wt. %, inparticular from 3.5 wt. % to 5.5 wt. %, in the reaction mixture haveproved favourable. In sustained operation the reaction generally takesplace at from 45 to 110° C., preferably 50 to 80° C.

The dissolved oxygen content in the reaction mixture for commissioningand in sustained operation is preferably less than 1 ppm, particularlypreferably less than 100 ppb. The dissolved or undissolved metal ioncontent of the reaction mixture for commissioning and in sustainedoperation is preferably not more than 1 ppm, particularly preferably notmore than 0.5 ppm in respect of Fe, Co, Ni, Mo, Cr, Cu as individualcomponents, and preferably not more than 10 ppm, particularly preferablynot more than 1 ppm for the total of the named metals.

A stratified bed reactor or fluidised bed reactor through which the flowis upward or downward and in particular a stratified bed reactor throughwhich flow is continuous from top to bottom is preferably employed asthe reactor.

The commissioning process according to the invention is suitable forboth the first start-up of a reaction system after changing the catalystand also for recommissioning, for example following a temporaryshut-down.

Commissioning with a reduced acetone concentration and an increasedphenol concentration is advantageous both when pure acetone/phenolmixtures are utilised and also in the industrially preferred operationof reaction units with recycled circulating streams containing phenol,acetone, BPA, BPA isomers and by-products and as an option water.

The advantage of the procedure according to the invention resides in theavoidance of irreversible damage to the catalyst resin, as a result ofcontrolling the acetone concentration, quantity and temperature. Suchdamage occurs when the catalyst system is commissioned with the acetoneconcentrations which are preferred in sustained operation, and ismanifested as mechanical damage to the catalyst beads and coloureddeposits on the surface of the catalyst beads. This damage leads toreduced catalyst activities and selectivities in sustained use and to anincreased pressure build-up in sustained operation, due to a change incompressibility. Increased coloration additionally arises in thecondensation reaction of phenol with acetone. The exclusion of oxygenand the control of the metal ion concentration in the reaction solutionensures that the activity of the ion exchanger is not impaired bydeposits of ionic constituents and that degradation phenomena due to theeffect of redox-active metal constituents and oxygen do not arise on theorganic matrix of the ion exchanger. Consequently, it is possible whenproceeding according to the invention to increase the BPA yield andquality in an industrially operated BPA plant, and to reduce the costlyreplacement of catalyst beds necessitated by deactivation.

The Examples which follow serve to explain the invention, which is notlimited to the Examples.

EXAMPLE 1

Sulfonated cross-linked polystyrene resin (Lewatit SC 104, from BayerAG) is utilised for industrial BPA production. The reaction system isoperated with a dewatered mother liquor from an installation to separatecrystals of BPA-phenol adduct, which is supplemented with phenol andacetone before entering the reactor. The typical composition, and thatwhich is optimal in terms of the acetone content in sustained operation,is:

phenol: 81.0%

acetone: 4.0%

p,p-BPA: 9.0%

isomers and higher condensates: 6.0%

water: <0.1%

The throughput in sustained operation is 0.3 m³ reaction solution/m³ ofcatalyst volume*h at an intake temperature of 58° C.

Following a catalyst change the reaction system is commissioned in thefollowing manner: the phenol-wet catalyst is transferred as a suspensionin phenol (70 vol. % solids) into the reactor (adiabatically operateddown-flow fixed bed reactor) at 60° C. Supernatant phenol is drawn off,and the catalyst bed is rinsed once with phenol (100 vol. %) and, afterthe phenol has been drawn off at the bottom, is charged up to the upperedge of the catalyst bed with phenol in counter-current. Reactionsolution then impinges at 58° C. on the catalyst bed. By admixing phenol(100 wt. %) to the reaction mixture which is normal in sustainedoperation, a reaction mixture of the following composition is adjustedby this means:

phenol: (90.5%)

acetone: 2.0%

p,p-BPA: 4.5%

isomers and higher condensates: 3.0%

water: <0.1%

0.06 m³ reaction solution/m³ catalyst volume*h (corresponding to 20% ofthe optimal throughput in sustained operation) flows in continuousmanner through the reaction system. The temperature profile is monitoredthrough the catalyst bed by means of temperature sensors at 20, 40, 60,80 and 100% of the catalyst bed height. A temperature peak occurs at 85°C. which is propagated through the catalyst bed and after 15 hours isrecorded at the outlet. At this time, the reaction mixture is adjustedat the reactor intake to the optimum values (4.0% acetone) for sustainedoperation, as indicated above. The throughput is then increased over thecourse of 40 hours in continuous manner from 0.06 m³ reactionsolution/m³ catalyst volume*h to the optimal quantity for sustainedoperation, 0.3 m³ reaction solution/m³ catalyst volume*h. The adjustedvalues are then maintained in sustained operation.

In sustained operation over a 60-day period a catalyst commissioned inthis manner demonstrates a 91% average acetone conversion and a 93.5%average selectivity for p,p-BPA formation from acetone. The averagepressure build-up through the catalyst bed was 0.2 bar/m. Catalystsamples taken from the top stratum of the reactor showed an averagebroken catalyst bead content of 5%.

COMPARISON EXAMPLE 2

The catalyst was commissioned as in Example 1, with the exception thatimpingement was directly with the optimal reaction mixture (4.0%acetone) for sustained operation at a throughput of 0.1 m³ reactionsolution/m³ catalyst volume*h, which was increased over a period of 5 hto 0.3 m³ reaction solution/m³ catalyst volume*h. Here, temperaturepeaks of 115° C. in the reactor bed were measured.

In sustained operation over a 60-day period a catalyst commissioned inthis manner demonstrates an 87% average acetone conversion and a 92.2%average selectivity for p,p-BPA formation from acetone. The averagepressure build-up through the catalyst bed was 0.3 bar/m. Catalystsamples taken from the top stratum of the reactor showed an averagebroken catalyst bead content of 15%. The catalyst beads were coveredwith a black surface deposit. Compared with the results from Example 1the colour of the reaction solution at the reactor outlet was increasedby an average of 5 Hazen units.

What is claimed is:
 1. Process for the commissioning of a process forthe production of 2,2-bis(4-hydroxyphenyl)propane by reacting phenolwith acetone in the presence of sulfonated cross-linked polystyreneresins, characterised in that a) the commissioning takes place with anacetone concentration reduced below, and a phenol concentrationincreased above, that of the optimal sustained operation state, with areduced quantitative throughput, and b) with temperature control, thereactant quantity and the acetone content of the reactor feed aresubsequently increased in step-wise or continuous manner until thesustained operating state is reached.
 2. Process according to claim 1,characterised in that on commissioning the acetone concentration islowered by 30% or more below the optimal concentration in sustainedoperation.
 3. Process according to claim 2, characterised in that oncommissioning the quantitative throughput is reduced by 40% or morebelow the optimal quantitative throughput in sustained operation. 4.Process according to claim 1 characterised in that the optimal acetoneconcentration in sustained operation is from 2.0 to 15.0 wt. %.